Antifoggevg and hardening agents for



United States Patent M ANTIFOGGING AND HARDENING AGENTS FOR PHOTOGRAPHIC EMULSIONS John Morgan and Donald Arthur John Starkey, Harrow,

England, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application September 16, 1953, Serial No. 380,586

, 13 Claims. (Cl. 957) No Drawing.

This invention relates to compounds useful as foginhibiting agents or hardening agents for photographic emulsions, and to photographic emulsions containing them.

I It is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during 1 graphic emulsions by storage at increased temperature or humidity, or both. It is of course desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be causedcby exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

It is, accordingly, an object of our invention to provide a method for stabilizing photographic emulsions. A :E urhardening photographic emulsions. Another object of our-invention is to maintain the sensitivity and fogof silver halide emulsions at or close to initial optimum values under keeping conditions of high temperature and humidity. A further object is to provide photographic silver halide emulsions containing antifoggants (or stabilizers) or hardening agents. Other objects will become apparent from a consideration of the following description and examples.

The above objects are, in general, accomplished by adding to the photographic emulsions at least one compound selected from those represented by the following two general formulas: Y 0

R-a-O (CH2CH20)-H and (2) I O O n-d-o -onzomo .-.-iin

2,732,303 Patented 24,

chloromethyl, bromomethyl, iodomethyl, dichloromethyl, dibromomethyl, diiodomethyl, trichloromethyl, tribromomethyl, ,triiodomethyl, u-chloroethyl, p-chloroethyl, a.- bromomethyl, fl-bromomethyl, fi-iodoethyl, etc. In the compounds selected from those represented by Formula 2, the R group can be the same or different.

The compounds selected from those represented by Formulas 1 and 2 above are, in general, known compounds. The compounds represented by Formula 1 above can advantageously be prepared by reacting a halogenated aliphatic carboxylic acid together with ethylene oxide in vary, in}; amounts. By varying the quantity of ethylene oxide, it is possible to produce monoesters wherein n has any desirable value. Accordingly, n can represent any positive integer, e. g., 1 to 200, or more. This method of making monoesters is well known and has been previously described in the prior art. Advantageously,.the reaction is carried out in the presence of an acidic catalyst, such as boron trifluoride (generally in the form of a complex, such as with acetic acid, diethyl ether, etc.).

The compounds embraced by Formula 2 above can advantageously be prepared by reacting together an acid halide (e; g. chloride, etc.) of a halogenated aliphatic carboxylic acid with asuitable glycol, such as ethylene glycol, diethylene glycol, triethylene glycol, the polyethylene glycols, etc. Thus, in Formula 2 above n can also represent any positive integer, e. g. l to 200 or more. The condensations can advantageously be carried out in the presence of an acid-bonding agent, such as pyridine, quinolinefetc although such acid-bonding agents need not be employed unless so desired. Also, if desired, an inert solvent, such as dioxane, diethyl ether, etc., can be employed.

wherein R represents a halogenoalkyl group, such as Alternatively, the compounds of Formula 2- can be prepared by heating together, in the presence of an acid esterification catalyst, a glycol, such as those listed above, with a halogenated aliphatic carboxylic acid. Suitable esterification catalysts comprises sulphuric acid, p-toluenesul.- phonic acid, etc. The speed of the esterification can be increased through the use of water-entraining agent, such as benzene, toluene, etc., which can be azeotropically distilled ofi.

When employing higher molecular weight glycols in the methods outlined above, a mixture of esters generally results. For example, when a large amount of ethylene oxideis employed with respect to the quantity of halogenated aliphatic carboxylic acid, the reaction mixture contains a mixture of esters wherein the value of n in Formula 1 varies. Likewise, when a polyglycol is reacted with a halogenated aliphatic carboxylic acid or carboxylic halide, a mixture of diesters wherein the value of n,varies, results. While it is sometimespossible to separatethese mixtures into the -cpmponent esters,- i t is not necessary, to do so. Accordingly, in the table given-below, in some cases only the average value of n is set forth. Mixtures of esters, or pure esters, can be'employed to advantage in practicing our invention. Mixtures of monoesters with diesters are also effective.

The following examples will serve to illustrate methods Triethylene glycol (30 gms. 0.2 mol.) was cooled to 0 C. in an ice-bath and redistilled chloracetyl chloride (54 gms. 0.48 mol.) added slowly with stirring. The temperature was kept below 20 C. during the addition, which was complete in about 20 inins. The solution was stirred for a further 30 minutes and the excess acid chloride removed by heating on the steam-bathat waterpump pressure. The viscous oil "ensued? 'B.-'-P. 22 8 230 C. /20 m m., yield 55 gms.. (91% theoretical).

Example 2.-Trie thyleneglycol-bis (p-chloropropionate) GhIOracetic acid (-19 gins. 0.2 inol.) was dissolved in sea: he (100 1111.) and boront'rifiuorideadd'e'd asth'e ether complex (-1 cc). Pure ethylene okide was passed into tlie-solnfidn ats 'e'h a 'ra't'ethat the temperature 'did not exee d 40 C. The new "of ethylene oxide was stopped "when an increase irrweight of 26 gms. was observed his. The excess ethylene oxide, benzene and any dioiane formed duringthe reaction were evaporated off on the steath batch, fi nally in Vao ubfor 1 hr. Yield "of Colourless -oi1 44 gms.

V In amanner similar to 'tlizit illlist'r'ated above in Examl to '3, "other monoand dies tei's coining Within the scope of general Formulas 1 and Zc'an be prepared. By usinglarger or smallermolar quantities of ethylene oxide than illustrated in E'iiample 3, it "is possible to obtain 'rnonoest'rs wherein the value of it in general Formula 1 has various values. Likewise by varying the glycol used inihe'methods described in Exampms 1 and 2, it is possible to obtain esters represented by general Formula 2 wherein n has various values.

Man "of the compounds sele cted from those represented by the Formulas land 2 above 'arewater'soluble. Those corr'ipoun'ds which do not have sufiicie'nt solubility in water 'ea'n be dissolved in alcohol solutions, such as ethanol, propanol, etc.

The fog inhibitors which we propose to use areadded to the emulsion during the process of manufacture, to avoidlossof sensitivity 'andto inhibit the growth of fog with passage of time under'nonideal conditions of "storage.

A solution of the "compounds of the invention when added in suitable concentration, before coating, to ims ensi tize d, chemically "sensitized, or optically sensitized photographic emulsions does not appreciably affect the 'sensitome'tric values for sensi'tivity'and fog when measuremerits are "madesoon after coating. When sensit om etric "measurements are made at "appreciable intervals 'of time,

"ah elevated temperatures and dry or-somewhat humid conditions, these "compounds do stabilize photographic speed and maintain fo' 'at a low level.

The preparation of-"silv'er halide emulsions involves three "separate'operations: l) the einulsific'ation and di- -'ges t io nor ripening of "the silver halide, (2) the freeing the emulsion fr'o'r'n 'eyiees's soluble salts, "usually 'by Wssh'i'sg and 53- the second digestion or after-ripening to obtain i er'asedsensi'tivity. (M'ees The Theory "of 'the Photographic Process, 1942.) We :prefer toadd the particularly useful when employed in'conjunction with --gelatino-silver -brorniodide emulsions, although they can also be jadvantageously employed for stabilizing other silver halide emulsions, such as -gelatino-silver chloride,

bromide, chlorobromide, chlorobromiodide, etc. The emulsions can b e unse nsitiz ed, or sensitized 'withch'emical sensitizers or -optical "sensitizeg l sulfur-sanitizers such as mose'ana sea in Sheppard U. S.;Patent 1,74,9 t4ean advantageously b eadded to t'he'iemulsioris in the"c61'1v'entional nia nner. "Alsofvarioiis"gold sfisitizers canbeem- '4 ployed in the photographic emulsions stabilized according to our invention.

The antifoggant or stabilizing activity of a number of compounds coming within the scope of general Formulas l and 2 was determined by incubation of a photographic emulsion at a temperature of 120 F. for three days at a relative humidity of 94% as shown in the table below. The efliciency of the various antifoggants was then evaluated by measuring the speed and fog of the incubated emulsions containing an antifoggant and comparing these measurements with those of the same batch of emulsion before incubation. Also, similar measurements were made on aphotographic emulsion containing no antifoggant, both before and after incubation. The tests were made using a high speed silver bromiodide emulsion exposed on an Eastman type Ib 'sen'sitor'neter with an exposure of second and then developed for five minutes in a developer of the following composition:

, g e. N-methyl-p-aminophenol sulfate Hydroquinone I 8.8 Sodium sulfite (anhydrous) 7 2.t) Sodium carbonate (cryst.) 2. 130.0 Potassium bromide 4.0 Water to make 1 liter.

TABLE I.'ANTIF OGG1ANT ACTION Ooneen- Initial Tests 3days 'Ex. com ound mum, incubagr/lnol' tlon fog AgX Speed Fog .18 1.54 as .12 .18 100 .19 2.32 100 .15 1.43 100 .19 2.32 .19 1.754 100 .21v 2.37 105 .-18 1.91 100 .10. 3. 50 100 .14 1.70 100 .34 52 100 .20 2. 35 100 .15 3.21 75 .16 2.45 100 .14 3. 46 .21 3.05 100 .08 3.16 105 .09 2.30

A llriethylencglyeol-bis (chloracetate).

' -'-=Triethyleneglycol-bis (fi-chloropropionate). .0=Polyethyleneglycol-bis (chloracetete),(n avg. 9).

D =.Tnethyleneglycol-mono (chloracetate) 'E= Ethyleneglycol-bls (chloracetnte) F =Tr1ethyleneglyc0l-bis (trichloracetate) .G Triethylencglycol-rnono (bromacetate). H=Polyethyleneglycol-mono (bromacetate) (71 avg. 60).

J=Polyethyleneglycol-mono (lodoaeetate) (n avg. 50).

-In a "manner similar to that illustrated in the above examples, other mono and diesters selected from --those rpres'ritcd by -the "above general formula can be incorporated in photographic emulsions for 'the purpose of stabilization. The fog-inhibiting agents useful in practieing our'inv'e'ntion can be used in various kinds of-photographic emulsions. In addition to being useful in-ordinaryfnon-sensitized emulsions, they can also be used in orthochromatic, panchromatic and -X-ray 'emulsions. -If used with sensitizing dyes, they can be added to the emulsion be'ftzireor "after the dyes -areadded. Suitable dispersing agents for the silver halide emulsions'stabilized according "to our invention comprisegelatin, -or other colloids, -such as collodion, albumen, cellulose organic "derivatives, synthetic resins, etc.

The optimum amount of fog-inhibitingagent can be determined by making the customary tests employed-in emulsion making. Of course, the optimum amount for a given emulsion will vary depending on the presence-of emulsion addenda, such as chemical sensitizers, optical sensitizers, etc. In general, we have found that from I 1.0. g. to 15 .O g. of fog inhibiting agent per mole of silver halide is sufficientfor the purpose of our' invention.

' Instead of adding 'the fog-inhibiting agent directly-to the photographic emulsion, it is sometimes desirable to incorporate the fog-inhibiting agent in a separate layer which is placed in contact with the silver halide emulsion layer which'is to be stabilized. Under such conditions, of course, it is advisable to use a higher concentration of fog-inhibiting agent than indicated above. In general, we have obtained excellent results .by simply adding a solution of the antifoggant in a suitable solvent, such as water, ethanol, propanol, etc. directly to the emulsion which is to be stabilized. This method is the one used in Examples I-IX above.

As noted above, certain of the antifogging compounds employed in our invention also have the property of hardening photographic emulsions. This effect for a number of compounds is summarized in the following table wherein the softening temperature of the emulsion containing no antifoggant is compared with a similar batch of emulsion containing an antifoggant, the determinations being made before incubation, after three days incubation at 120 F. and a relative humidity of 94%, and after seven days incubation at 120 F. and a relative humidity of 42%. The results are summarized in the following table.

K=Polyethyleneglycol-bis (chloracetate) (n avg.

L:Polyethyleneglycol-mono (chloracetate) (12 avg. 6). M=Triethyleneglycol-bis (bromacetate) Tables I and II above show the antifoggant activity and hardening action of a number of compounds embraced by our invention. In like manner, other compounds selected from those represented by Formulas 1 and 2 above can be employed to provide the advantages of our invention.

What we claim as our invention and desire secured by Letters Patent of the United States is:

1. A photographic silver halide emulsion containing at least one compound selected from the group consisting of those represented by the following two general formulas:

o o R-( O (-CHgOHzO)-2R wherein R represents a halogenated alkyl group containing from 1 to 2 carbon atoms and n represents a positive integer.

2. A photographic silver halide emulsion containing at least one compound selected from the group consisting of those represented by the following two general formulas:

O R-ii0 (-0H,0HlO).-H

and

O 0 R-Ji-O (-CHzCHiO)nP/R wherein R represents a halogenated alkyl group containing from 1 to 2 carbon atoms and n represents a positive integer of from 1 to 200.

3. A photographic gelatino-silver halide emulsion con- 6 taining-at least one compound selectedfrorn those represented ;by the-following general formulas" n-g-m-omommrn I wherein R represents a halogenated alkyl group containing from 1 to 2 carbon atoms; and n represents a positive integer of from 1 to 200. 4. A photographic gelatino-silver halide emulsion containing at least one compound selected from those represented by the following formula:

wherein R represents a halogenated alkyl group containing from 1 to 2 carbon atoms and n represents a a positive integer of from 1 to 200.

5. A photographic gelatino-silver halide emulsion containing at least one compound selected from those represented by the following general formula:

wherein R represents a chlorinated alkyl group containing from 1 to 2 carbon atoms and n represents a positive integer of from 1 to 200.

6. A photographic gelatino-silver halide emulsion containing at least one compound selected from those represented by the following general formula:

wherein R represents a halogenated alkyl group containing from 1 to 2 carbon atoms and n represents a positive integerof from 1 to 200.

8. A photographic silver halide emulsion containing at least one compound having the following formula:

9. A photographic silver halide emulsion containing at least one compound having the following formula:

10. A photographic silver halide emulsion containing at least one compound having the following formula:

0 o l oi-omiii-o omomo),.isorig-o1 wherein n has an average value of 9.

11. A photographic silver halide emulsion containing at least one compound having the following formula:

12. A photographic silver halide emulsion containing at least one compound having the following formula:

O 0 R-il-0 -cHon,o)..ii-R wherein R represents a halogenated alkyl group containingfrom l to 2 carbon atoms and n represents a'positive integer.

References Cited in the file of vthis patent UNITED STATES PATENTS Simmons Apr. '29, I941 Weissberger et a1 Aug. '22, I944 Fallesen June '12, 1945 Blake "May 11, 1948 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF THOSE REPRESENTED BY THE FOLLOWING TWO GENERAL FORMULAS: 